Advanced imaging modalities and new chemotherapy drugs are driving down cancer deaths, according to a new study, buttressing arguments that expensive advanced imaging is worth its cost.

A study released by the National Bureau of Economic Research, a think tank, argues that the growth in use of MRI and CT scans, as well as advances in anti-cancer medicine, has added three months to life expectancy at birth for Americans during the period under review, from 1996 to 2006.

About 40 percent of the almost 13 percent decline in cancer mortality from that period is attributable to the adoption of advanced imaging systems, according to the study's author, Dr. Frank Lichtenberg, a business professor at Columbia University in New York.

"The debate has been whether using these advanced diagnostic imaging techniques is worthwhile - do they lead to better outcomes? My study suggests they do lead to better outcomes," Dr. Lichtenberg told DOTmed News by phone from Melbourne, Australia, where he's a visiting professor at Victoria University.

For the study, Dr. Lichtenberg examined data on over 60 sites. One source was the National Cancer Institute's Cancer Query System, a national database that tallies cancer deaths. He compared cancer deaths at these sites with usage of advanced imaging modalities, such as MRI and CT scanners, in place of standard X-ray imaging. He found information on modality use by checking the MEDSTAT MarketScan database, which compiles statistics from employer-sponsored health plans.



Dr. Lichtenberg also used the MEDSTAT database to check the rate at which the sites administered new chemotherapy drugs made available in the 1990s, such as docetaxel, approved by the FDA in 1996.

Dr. Lichtenberg reasoned that sites with above average use of advanced imaging would see a higher-than-normal reduction in age-adjusted mortality from cancer, albeit with a delayed effect. Presumably, the life-saving effect of imaging modalities, which help doctors catch and treat cancers earlier, would be "lagged"; but they would see an immediate death reduction for use of the new breed of cancer-killing drugs.

And that's exactly what he found. "I do observe essentially that the cancers where there has been the most innovation have seen the largest reductions in mortality," Dr. Lichtenberg said.

Of the nearly 13 percent drop in age-adjusted mortality rates between 1996 and 2006, Dr. Lichtenberg discovered that the lagged effects of advanced imaging accounted for nearly 40 percent of the decline, with drug innovation accounting for around 27 percent of the drop. Although the incidence of cancer declined in this period, too, this only accounted for around 7 percent of the decline in mortality, Dr. Lichtenberg observed.

Intriguingly, by his estimates, Dr. Lichtenberg suggests that advances in imaging have so greatly impacted cancer survival, they could be responsible for nearly 9 percent of the decline in mortality from all causes in the period studied.

OVERCOMING BIAS

Dr. Lichtenberg's research contradicts earlier findings that suggested new drug advances and the adoption of new imaging modalities made only a small dent on cancer death rates. But Dr. Lichtenberg said by counting up all deaths from cancer at the sites instead of relying on a 5-year survival rate, which some earlier studies used, he was able to avoid one of the great plagues of long-term cancer research, the so-called lead time bias.

"There's this issue that if you have advances in diagnostic techniques, people might appear to live longer after diagnosis, but only because they're diagnosed earlier. I avoid that problem by looking at the unconditional mortality rate -- simply looking at how many people die from each type of cancer, rather than the probability of dying within 5 years of diagnosis," Dr. Lichtenberg said.

Still, he admitted the data might not be entirely free from error. The incidence of cancer was determined using NCI's data set, which only represents about one-quarter of the U.S. population, and might be subject to sampling errors, he said. And the data on diagnostic imaging and pharmaceutical usage come from MEDSTAT, which excludes Medicare patients, the most likely to require advanced imaging and come down with cancers. Nonetheless, Dr. Lichtenberg does not believe this would have skewed the results.

"Even if there tended to be a difference in survival trends between elderly and non-elderly, that would not result in any bias, unless that difference varied across cancer sites in a way that was correlated with treatment innovation," he said. "I don't think there's any compelling reason to think there would be such a bias."

The study was funded in part by Siemens, an OEM that makes advanced imaging devices, although in the paper the author said the company did not try to influence the research in any way.

Imaging lobbying groups have welcomed the study. "The Access to Medical Imaging Coalition commends Dr. Lichtenberg for confirming what cancer survivors and the medical imaging community have known for many years -- advanced imaging saves lives," Tim Trysla, executive director of the coalition, said in a statement. "We must continue to support efforts to preserve access to life-saving imaging services, encourage innovation and improve patient care."